An Update: I've experienced much-improved performance with the "retail build" currently out, but that build is two weeks older than the dev build that, for me, brought all of the issues out in the first place. I fear that, when the backlog of dev "fixes" are brought back, it may go back to slideshow territory.
In the meantime, however, I found that I was able to cheat an extra 25 to 30fps out of the game doing three things One, open the task manager and set the Arma III process to highest, two, lower SSAO to "standard", and three, reduce my view distance from the auto-detect setting of 3800 to 3000. I went from 30-35 fps (on the retail build!) to 55-60fps! I saw drops into the 40s when entering towns and such, but it's a MASSIVE improvement over what I had last week!